Wiring A Kitchen

[andyth]

I have been renovating my kitchen and have equipped it with 4 double sockets. I now realize that the wiring supplying the kitchen (2 X 2.5 sq. mm. plus earth) is inadequate to meet maximum possible demand. If every appliance in the kitchen were switched on at the same time ( fridge/freezer, kettle, microwave, mini-oven and twin-plate hob) the power consumption would be around 8.5 kilowatts or 39 amps. My question is what size cable should I use to supply the power, bearing in mind that it would be fairly rare for everything to be switched on at the same time. The kettle would be on only briefly, so a more realistic maximum continuous load would be 32 amps. Can any qualified electrician tell me whether 4 sq mm be enough, or should I go for 6 sq mm? My intention is to connect the cable to a dedicated MCB on the consumer unit. I could wire the hob (3.5 kilowatts) separately but I'd prefer not to.

[Crossy]

It is not wise / safe / legal to simply put a bigger wire and breaker.

The reason is that, because we don't use UK style fused plugs any potential fault current from an internal appliance fault must pass down the appliance flex which may have too high a resistance to pull the breaker, result = overheating flex and possibly fire!

The correct solution is to add more 20A breakers with 2.5mm cables and feed say, two double outlets off each. This will have the additional benefit (if you do it right) of isolating your freezer from the possibility of nuisance trips.

Since you're going to have to pull a new cable anyway, why not do it properly

[funfun]

It is not wise / safe / legal to simply put a bigger wire and breaker.

The reason is that, because we don't use UK style fused plugs any potential fault current from an internal appliance fault must pass down the appliance flex which may have too high a resistance to pull the breaker, result = overheating flex and possibly fire!

The correct solution is to add more 20A breakers with 2.5mm cables and feed say, two double outlets off each. This will have the additional benefit (if you do it right) of isolating your freezer from the possibility of nuisance trips.

Since you're going to have to pull a new cable anyway, why not do it properly

here here, now youve listed all the appliaces you will need, dont forget to ask her or him or whoever else will use the kitchen what THEY will use, maybe a tv or rice warmer cooker music (hi fi), phone chargers (they dont take a lot but they plug in) maybe light outside kitchen door or soket for garden etc and add an extra socket or 2 on for good mesure.

as the post above says, if youre gonna do it, do it right, then its only once!

good luck.

[andyth]

The correct solution is to add more 20A breakers with 2.5mm cables and feed say, two double outlets off each. This will have the additional benefit (if you do it right) of isolating your freezer from the possibility of nuisance trips.

Since you're going to have to pull a new cable anyway, why not do it properly

Thanks very much for your advice. Perhaps I could draw further on your expertise. I should have said in my original posting that the four double sockets and the hob are connected to a small consumer unit in the kitchen with 3 MCB's of 16 amps each. The hob is fed through one of them and each bank of 2 double sockets is fed by each of the other 2 MCB's. So my question still concerns the size of cable to the small consumer unit in the kitchen. As I live on the top floor of a 4-story block I have access to the roof space, where all the wiring is, but the conduit that houses the wiring to the kitchen is not large enough to take 2 or 3 2.5mm sheathed cables plus an earth cable. The other problem with several 2.5mm cables going back to the main consumer unit is that there is only one spare MCB slot left.

[Crossy]

Thanks very much for your advice. Perhaps I could draw further on your expertise. I should have said in my original posting that the four double sockets and the hob are connected to a small consumer unit in the kitchen with 3 MCB's of 16 amps each.

YES, you should have specified this 'minor' point in the OP as we are now in a different realm

Use these sizes as a guide:-

The following shows the cables sizes for the appropriate circuit breaker;

1.5 mm2 cable - 15 amp maximum circuit breaker.

2.5 mm2 cable - 20 amp maximum circuit breaker.

4 mm2 cable - 25 amp maximum circuit breaker.

6 mm2 cable - 32 amp maximum circuit breaker.

10 mm2 cable - 40 amp maximum circuit breaker.

If I was you I'd pull 6 or 10mm (if it will fit in the conduit) use individual building wires rather than sheathed as they will take less space but only do this if the run is completely enclosed in conduit.

In your CU protect the new cable with a breaker of appropriate rating as above.

Edited June 20, 2007 by Crossy

[andyth]

If I was you I'd pull 6 or 10mm (if it will fit in the conduit) use individual building wires rather than sheathed as they will take less space but only do this if the run is completely enclosed in conduit.

In your CU protect the new cable with a breaker of appropriate rating as above.

Thanks again for your advice. Apologies for the vital omission in my original post.